High-frequency triode oscillator



Nov. 19, 1946.

D. H. SLQAN 2;411; 299

HIGH FREQUENCY TRIODE OSCILLATOR' Filed Nov. 12 1941 s Sheets-Sheet 1 INVENTOR. DA v10 H. SLOA N A TTORNEYS.

Nov. 19, 1946. D. H. SLOAN HIGH FREQUENCY TRIODE OSCILLATOR Filed Nox l. 1941 6 Sheets-Sheet 2 FIE-,7

INVEN TOR. DA v10 H. 81. OA-N BY W? Z.

ATTORNEYS.

Nov. 19, 1946. D. H. SLOAN I 2,411,299

HIGH FREQUENCY TRIODE OSCILLATOR Filed Nov. 12, 1941 6 Sheets-Sheet 3 INVENTOR DA VID h. SLMN BY JE W o ff ATTORNEYS.

Nov. 19, 1946. D. H. sLoAN 2,411,299

HIGH FREQUENCY TRIODE OSCILLATOR Filed Nov. 12, 1941 6 Sheets-Sheet 4: I

2 Lona Ac INPUT INVENTOR. Dawn H. SLonlv Nov. 19, 1946. D H, mm 2,411,299

HIGH FREQUENCY TRIODE OSCILLATOR Filed NOV. 12, 1941 6 Sheets-Sheet 5 zrr .FJ" Eli; za: 0 209 2 H IN VEN TOR..

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NOV. 19, 1946. SLQAN 2,411,299

HIGH FREQUENCY TRIODE OSCILLATOR 7 Filed Nov. 12, 1941 Sheets-Sheet 6 Dav/0 H. 81.04

f M W} ATTORNEYS.

Patented Nov. 19, 1946 2,411,299 HIGH-FREQUENCY TRIODE OSCILLATOR David H. Sloan, Berkeley, Calif., assignor to Research Corporation, New York, N. Y., a corporation of New York Application November 12, 1941, Serial No. 418,669

36 Claims. 1

My invention relates to electronic tubes of the triode type and more particularly to high power tubes peculiarly adapted to the production of ultra-high-frequency oscillations, i. e., oscilla tions having wavelengths from to centimeters for example. I'his application is a continuation-in-part of my prior application Serial No. 364,284, filed November 4, 1940.

In the recent progress of electronic and radio development there has been an increasing demand for oscillation generators combining highpower output with micro-wave oscillation generation. These two requirements have been, to a certain extent at least, incompatible, and a large amount of research has taken place to the end that these two factors might be reconciled in order to produce practical apparatus which will have a high-power output at extremely short wavelengths.

In my previous application cited above I have shown, described and claimed a tetrode structure which is capable of producing many kilowatts of power at wavelengths within the micro-wave range. My present invention is a simplified improvement on the tube of that application, in that I have been able to produce a triode tube capable of generating a large mount of highfrequency power. For example, 100 kilowatts of oscillation power having a l5-centimeter wavelength can be produced with the preferred form of tube of my invention, herein to be described, using a 60,000-volt anode excitation.

It is the broad purpose, therefore, of my present invention to provide a simple, compact and easily assembled electronic tube structure of the triode type, completely reconciling the apparent incompatible factors of the production of large amounts of power at relatively high frequencies.

As a result of this general purpose, therefore, several objects of my invention are: To provide a triode tube which is capable of producing tens of kilowatts of power at extremely high frequencies; to provide a high-frequency oscillation generator of great frequency stability; to produce a high-frequency oscillator tube of relatively high efliclency, and particularly to produce such a tube wherein the losses due to undesired radiation from the tube itself are reduced to negligible proportions; to provide a novel means and method of terminating a resonator or transmission line; to provide a high-frequency oscillation generator of relatively large physical size, as compared to the wavelength of oscillation; to provide an electronic triode tube of the character described which may be fully fluid cooled, and

tube operating at relatively high frequencies;

to provide a novel means and method of operating a high-frequency oscillation generator of the triode type; to provide a simple system of resonator chokes for use in preventing undesired radiation from a self-resonating oscillating triode;

to provide a means and method of operating a triode to obtain maximum power output at high frequencies; to provide a simple electronic tube incorporating a resonator, which can be operated as an oscillation generator; to provide a tunedfilament tuned-anode oscillator operating with capacity feedback; to provide a triode oscillator operating on a half-cycle work period, or multiple thereof; and to provide an electronic triode of rugged and simple construction which, when energized, can be utilized to produce tens of kilowatts of power at relatively high frequencies and short wavelengths, such as, for example, from 10 to 20 centimeters.

My invention possesses numerous other objects and features of advantage, some of which, together with the foregoing, will be set forth in the following description of specific apparatus embodying and utilizing my novel method. It is therefore to be understood that my method is applicable to other apparatus, and that I do not limit myself in any way to the apparatus of the present application, as I may adopt various other apparatus embodiments, utilizing the method within the scope of the appended claims.

The triode tube of my present invention embodies several basic concepts.

The first basic concept is the provision of a simple resonator having spaced opposing walls carrying a D.-C. diiference of potential, and wherein the cathode is attached to one wall with .the opposing wall acting as an anode. Grid surfaces are inserted between cathode and anode for controlling the effect of the A.-C. and D.-C. fields on the electrons. The grid surfaces may be extended to separate the resonator into two resonant regions, if desired.

A. second basic concept of my invention is the arrangement and tuning of separate resonator compartments, if used, in such a manner that the tube can oscillate in a tuned-filament, tunedanode circuit with capacity feedback, with or without the aid of electromagnetic feedback. The circuits are tuned so that the grid and anode oscillate positively with respect to the cathode at the same time. If only a single resonator is used, the electrode voltages are divided to cause the tube to oscillate in a similar manner. I prefer to use a finite transit time, i. e., an electron work cycle of one or more half cycles, preferably a single half cycle.

It is practical to make the tube of my invention of relatively large size evenfor very short wavelengths, as the transit distance may be oneeighth wavelength. Thus, in a. tube operating at 16 centimeters, for example, the spacing between grid and anode surfaces may be approximately 2 centimeters.

The third basic concept comprises forming electrodes of sturdy coaxial metal containers, which form a radio-frequency resonator, or resonators, full D.-C. insulation being maintained between these elements. D.-C. insulation demands gaps, through which radiation is reduced to a negligible factor by a choke system formed by a sequence of anti-resonant high impedances and quarterwave low impedance lines.

In the ensuing specification, my invention will be described in its various aspects as applied to an oscillator tube of high power, i. e., approximately 100 kilowatts peak output at 15 centi- Fig. 4 is a sectional view taken as indicated by the line 44 of Fig. 1.

Fig. dis an enlarged showing of variable electromagnetic feedback structure usable in the tube of Fig. 1.

Fig. 6 is a partial view showing a fixed electromagnetic feedback usable in the tube of Fig. 1.

Fig. 7 is a diagram showing how the tube of my invention can operate with all but the electron interaction field determining elements removed from the grid.

Fig. 8 is a sectional view taken as indicated by the line 8-8 in Fig. 7.

Figs. 9, 10 and 11 are diagrammatic views showing modifications of resonator choke systems. 4

Fig. 12 is a sectional view of a means of measuring the power output of the tube of my invention.

Fig. 13 is a sectional view taken as indicated by line 'I3I3 in Fig. 12.

Fig. 14 is a partially diagrammatic sectional view of a modification ofmyinvention.

. Referring directly to Fig. 1 for a-detailed description of my invention, a filament support port It the coaxial ducts are separated into reflexed portions I2, flexible to permit axial expan sion of filaments to be attached to the inner end of support III.

At the inner end of the central cathode support I0, is fastened a circular filament support flange I4 in which the ducts in support I6 and pipe I I are connected. A cathode resonator end element I5 is mounted on flange I4 to extend axially beyond flange I4.

concentrically positioned around central filament support I6 is an outer filament support I6, the two supports I0 and I6 being outwardly provided with lateral sealing flanges l1 and I9, respectively, connected by an insulating cylinder 20, such as a glass cylinder, the latter holding the supports in concentric relation, using metalto-glass seals. Sealing flange I! is attached to support I0 outside of reflexed portions l2. Demountable seals can, of course, be used in conjunction with continuous pumping. The inner end of outer cathode support I6 is provided with a circular filament support flange 2|, positioned parallel to and axially spaced from filament support flange I4.

The cathode support I6 is preferably formed of two telescoping tubes I6 and II, the inner tube I'I having opposite channels I8 cut therein. These channels I8 are connected in support flange 2I at one end thereof and to inlet and outlet pipes I9 and 26 at the opposite end, as shown in Figs. 3 and 4, these pipes passing laterally then outwardly through sealing flange I9 and sealed thereto at right angles to loops I2. Thus, both filament support flanges I4 and 2I can be cooled from outside the tube by a circulating fluid, such as water.

Inner and outer cathode supports are spaced by quartz positioning pins 22 between filament support flanges I4 and 2|. The space between flanges l4 and 2I is closed by extensions 23 and 24 extending from central cathode support I6 and flange 2I, respectively, and overlapping in the midplane intersecting the filaments, without touching. The quartz pins 22 are attached to extension 23, and extension 24 is apertured to allow pins 22 to contact cathode support I0.

Filament flanges I4 and 2I are joined by a plurality, preferably twelve in the present instance, of U-shaped, axially extending filaments 25, these filaments being provided with flat or slightly con- 1 describe a cylindrical surface.

structure is utilized comprising a central cathode cave surfaces facing outwardly, as has been described in my prior application cited above. The filaments are preferably of heavy tungsten and are arranged to have the outer surfaces thereof Between central cathode support Ill and outer cathode support I6 are positioned a pair of filament supply chokes 26 and 21, preferably mounted on support III, the action of which will later be described in conjunction with the action of other, and somewhat similar chokes used in the tube.

A grid cylinder 36 is provided, enclosing outer cathode support I6 and cathode resonator element I5, and spaced therefrom by the use of an outer grid'seal flange 3| joined to the cathode seal flange I9 by an insulating glass sleeve 32, using Inetal-to-glass seals. Here again demountable seals may be used, if desired. Grid cylinder 36 is provided ith an inner end 33 spaced from and surrounding cathode resonator element I5. The grid cylinder is also provided with slots 35 milled therethrough opposite each filament 25. Other grid constructions providing equivalent electron interaction field control may be utilized and are deemed full equivalents. The outer portion of the grid 30 and its sealing flange 3| and the portion of the cathode support flange IS, inside of insulator may be apertured for vacuum communication through the tube.

The flat or slightly concave surfaces of the filaments are preferably positioned a few thousandths of an inch back of the slots in the grid cylinder to permit insertin the filament group inside of the grid. The grid slots are properly shaped and positioned to distribute the field as uniformly as practical over the cathode surfaces at the time of maximum emission, and to direct these fields then toward the anode, with the distance from the emitting surfaces to the sensibly always uniform field beyond the grid only a small fraction of the anode-cathode distance.

An anode 31 is provided, also a cylinder having a domed end 38, and is positioned around the grid, although in this case the outer end of the anode terminates a substantial distance away from the grid seal flange 3| inorder to provide space insulation. An outer anode seal flange is prochoke system acts as a part of the resonator which when thus augmented, is really short cirvided, joined with metal-to-glass seals to the grid flange 3| by an exterior relatively long high-voltage insulating sleeve 4|, or, if desired, with a demountable seal. The tube may be continuously exhausted through a vacuum line attached to the grounded anode of Fig. l or through a sealed 01f glass connection 42 if the tube is to be used as a sealed tube.

The anode is provided with a narrow space water jacket 43 surrounding the impact area of electrons coming from the filaments after passing through the grid slots 35. This water jacket is provided with triple inlets 44, and opposite triple outlets 45, so that water may be passed around the anode at high velocity to effectively cool the anode.

Cathode resonator chokes 46 and 41 are positioned serially on outer cathode support l6, and anode resonator chokes 48 and 49 are positioned serially on grid 30, to terminate the cathode and anodes in a high impedance, as will later be explained, with full D.-C. insulation between cathode, grid, and anode. Cathode supply chokes 26 and 21, cathode resonator chokes 46 and 41, and anode resonator chokes 48 and 49 are all antiresonant systems with the two chokes of each sys- I tem joined by quarterwave line sections.

Each comprises, in the tube of Fig. 1, laterally extended flanges 5| attached centrally to the supporting electrode, carrying outer cylindrical portions 50 spaced from, but positioned close to and concentric with, the wall of the opposing electrade. The positioning and function of these chokes will later be described in detail.

I may prefer to mak the cathode resonator choke systems 46 and 41 movable for tuning purposes, and therefore mount both of these chokes On a sleeve 52 sliding on outer filament support It, the inner end of this sleeve terminatil'lg in the same plane as the'inner end of the cylindrical portion of choke 46. The two chokes joined by this sleeve may be axially moved by a rod 53 extending axially along the space between the outer filament support l6 and the grid 30, and then bending outwardly to pass axially again through an opening 54 in the cathode seal flange [9. The rod is fastened to an end plate 55 attached to cathode flange Is by a metal bellows seal 56, the position of end plate 55 being regulated by end plate positioning screws 51. The vacuum within the tube tends to collapse the bellows, and the screws prevent this collapse.

' line 6| has a central cuited to R.-F. at this extreme end.

The ends of the resonators opposite the closed ends I prefer to call the open or open-circuited ends of the resonators, as the resonator spaces are there continuous over the ends of the resonator conductors and the conductors are electrically open-circuited at this extreme end The cathode resonator resonator element l5 and grid-end 33, to terminate at their open end, and likewise the anode resonator is continued to an open end termination by the portion of the grid extending around cathode resonator element l5, and the end 38 of the anode. Thus, th two resonators have a .common wall, i. e., the grid. The completed resonators are both designed to resonate at the same odd number of quarter wavelengths, preferably five in the tube being described, with a particular filament and grid slot location, as will be brought out later.

The output of the tube is preferably taken through an output transmission line 6| inserted through anode 31 at a current loop. The output conductor 62 extending as a loop into the anode-grid space and then returning to contact th outer conductor of the line. This transmission line may then be used, as is well known in th art, to supply any load as maybe desirable. The line may be sealed from the atmosphere by an insulating barrier 63 positioned at a voltage node.

Inasmuch as one of the main uses for a tube of this type is for the production of maximum quantities of oscillating power at low wavelengths, the anode may be energized without external rectifiers, using raw A.-C. I have shown in Fig. 1 one circuit by which the tube has been successfully operated as a self-rectifying oscillator.

A filament transformer is provided, the secondary 8| of which is attached" to central cathode support H1 and to cathode flange 9. Transformer B0 is excited through a primary 82 supplied from the A.-C. main 83. A.-C. mains also supply a high voltage anode transformer 85 through primary 86, the secondary 81 having one end connected to the anod flange 40 and thus to the anode 31. The anode end of the anode transformer is grounded, the anode operating at ground D.-C. potential, providing a grounded anode tube in this embodiment of my invention. The other end of the anode transformer secondary 81 is connected through a resistor 89 to one side of the cathode, such as, for example, flange I9. Grid bias for field control is obtained by a connection 90 on the grid flange 3| to some point on the resistor 89 as may be found desirable. This bias may be from -3000 on the operative portion of the supply cycle.

Before passing to the geometry of the resonators, a discussion of the means and. method by which I effectively close the resonators to R.-F. with full D.-C. space insulation is first in order. As a first premise, the outer ends of the filament supports, grid and anode, can be considered as antennae, ready and willing to radiate if energy escapes to those ends. Such radiation may be is projected by cathode volts negative,

taken to be a loss load, and should be reduced to a negligible factor. For purposes of discussion, therefore, the outer portions of the chokes or choke systems can be spoken of as the load ends thereof, and the inner portions as the input ends thereof.

Before discussing the physical shape the choke systems may assume, as these shapes may be several, the operation and theory of the choke systems will be briefly set forth. The problem is, of course, to terminate the transmission lines, as the anode and cathode resonators are true transmission lines, without substantial loss of energy past the terminations, meanwhile maintaining complete D.-C. insulation between the walls of the lines or resonators.

Obviously, a transmission line can be terminated by a conductive barrier connecting the inner and outer conductors, thus providing zero impedance across the line. Such a barrier would not, of course, permit any D.-C. difierence of potential between the line conductors in this first method.

A second type of termination would be a termination of infinite impedance, such as if a line conductor were to be completely cut off at the desired point. However, such a cut-off would revent support between the cut-off portions and prevent metallic connection to maintain a D.-C. potential.

My preferred and practical method of resonator, combines the D.-C. insulation, D.-C. connection, and physical support. It will be described as an alteration of type one, and then described as an alteration of type two. Both viewpoints are essential.

Viewed as a modification of the first or shortcircuited termination for preventing the escape of radiation, the conductors are metallically joined, and D.-C. insulation is provided by cutting open one conductor of the line at a current node and bridging this cut by a very low impedance which is formed by the input end of a quarterwave line whose distant open load end terminates in a high impedance. Almost negligible power will flow into this line because negligible current fiows through its almost negligible input impedance. This low impedance is made of two insulated conductors forming the quarterwave line, thereby providing D.-C. insulation where the low impedance is connected into one of the resonator conductors. This connection occurs one quarter wavelength away from the short circuit that suggested the name closed for this end of the resonator.

The second viewpoint considers the resonator line terminating in an open circuit at the same point where it was cut to insert the low impedance quarterwave line connection of the first method. The quarterwave section beyond this cut is now considered asa choke in series with the low impedance quarterwave line, and together they act as the high impedance termination of the resonator which now ends at the cut and is a quarterwave shorter than the resonator in the first viewpoint. Thus the short-circuited end section of the resonator beyond the cut may be considered as part of the resonator in the first view or as the first choke in the high impedance termination of the second view. Its variation of impedance with frequency makes it important in the tuning of the resonator. Subsequent descriptions will follow this second viewpoint, having the open circuited line terminated by a chokeline-choke combination.

Movement of the position of the choke-linechoke system for the purpose of tuning may be considered as varying the amount of conductor existing in the resonant line up to the point where it is cut for insertion of the low impedance of viewpoint one, or cut for high impedance termination of viewpoint two.

The voltage across the input choke is as high as the standing wave voltage at the end 01' the last quarterwave section of the line, and the antiresonant impedances are similar. Therefore, the energy stored in the choke is as great as the energy in the adJacent quarterwave section of line to be terminated.- Thus, the input choke adds an effective quarter-wavelength to the system of standing waves in the line. As the standing wave loop appears at the end of the line the position of the choke system along the line can be used to tune the line.

In the second view, one conductor of the resonant line is provided with a physical out which is bridged by a quarter wave anti-resonant choke, with the provision of a second out at the end of an electrical quarter wave continuation of either of the line conductors toward the load and the provision of a similar choke bridging the second cut. Thus, the intermediate quarter wave line section terminates in a high impedance making the input to this quarter wave line have very low impedance. This very low impedance appears in series with the high impedance of the first quarter wave choke, and both impedances are connected directly across the end of the line which is to be effectively opened. The high impedance limits the current which can fiow through the low impedance hence very little power enters the low impedance line to escape from the resonator. The input side .of the line leading to such a choke system is now effectively terminated by a nearly infinite impedance, and only a standing wave voltage 100p can appear at the end of the line. Thus, from the second viewpoint, I have provided a practical equivalent of a physical open circuited end of the input line, meanwhile maintaining D.-C. connection, full support of the conductors, and D.-C. insulation between line conductors.

While there are a large number of physical structures which will provide a choke system operating as above described, I first wish to describe a toroidal form of choke system, inasmuch as this type of choke system clearly illustrates successive conductor separations, these separations being joined by solid choke members.

Referring, therefore, first to Fig. 9, a transmission line having closely spaced inner and outer conductors and 9| having an input end 92 and a load end 93, is diagrammatically illustrated with the chokes positioned inside the inner conductor, although either conductor may be used. Toward the input end, the inner conductor is physically cut to provide a gap 94. The two physically cut ends of the line are then joined by a toroidal, anti-resonant high impedance input choke 95.

On the load side of the high impedance input choke, the inner conductor is continued as an electrical quarter wave line section ending at a second gap 96 in the conductor which is bridged by a second toroidal choke 91 similar to the first. Full physical support, therefore, is given to the input end of the inner conductor from the load end through the chokes, with loss toward the load end reduced to a negligible factor and with the complete D.-C. insulation between the line members, as above described.

While such toroidal chokes may be used in conjunction with the tubes herein described, where room for insertion is available, such as extending outwardly from the anode for example, I may prefer to utilize other and fully equivalent forms of choke systems, particularly if tuning of the associated resonators is desired, as by moving the choke systems along the line.

In Figs. 1, 10, and 11, I have shown equivalent resonator terminal systems. In these, the crosssection of the concentric lines is changed by additional conductors supported by a continuation of one of the conductors, this continuation no longer forming a part of the standing wave area of the line. The line formed by the additional conductors may then be cut and the cuts bridged by chokes, as hereinafter described. These systems are used to terminate the cathode and anode resonators of the tube heretofore described.

In Figs. 1, 10, and 11, I have shown different forms of cylindrical choke systems, each comprising two anti-resonant chokes, spaced by quarter wave transmission lines. In Fig. 1, the cathode choke system 46-41 is shown movable and with the separate chokes opening toward the filaments, While the anode choke system 48-49 is shown fixed in position and opened in the same direction. In Fig. 11, all of the chokes are shown fixed in position but opening away from the filaments. Fig. 10 shows an intermediate step.

First, I wish to discuss the type of choke system shown in Fig. l where the chokes open into the associated resonator'spaces, either as moviable or fixed systems. In case a fixed choke system is desired, the choke flange of each choke may be rigidly attached to the supporting element by welding, silver soldering, brazing, etc., at a current loop. The free edges of the cylindrical portions areat voltage loops. When fixed chokes are used, the connection of the flange to its supporting element at a current loop is not a disadvantage as conduction between flange and supporting member will be good.

When a, movable system, however, such as system 46-41 in Fig. 1 is utilized, if no sleeve 52 were to be utilized, there would be a high current density and high resistance between the sliding contact of the flange 5| and the supporting mem-- ber, particularly at the flange closest to the resonator space. However, when sleeve 52 is used and the sleeve extended along the supporting member to terminate at the same level as the free edge of the cylindrical portion, the free end of the sleeve is at a current node and the resistance losses are low.

It will be noticed that, when this type of choke system is utilized, there may be, in an extremely high powered tube where the inner conductor of a line resonator is of small diameter compared to the diameter of the outer conductor, high densities on the inner conductor, as for example the outer filament support In in the tube of Fig. 1. The current has to pass along this support to reach the flange 50 of the input choke. In order to reduce this high current density, it may be desirable to effectively enlarge the diameter of the support I!) at positions of heavy current concentration.

This effective increase in diameter can be accomplished, for example, by increasing the size of a quarter wave section of the support II] with a closed end cylinder 98 until the exterior surface thereof approaches the grid 30, as shown diagrammatically in Fig. 10. When this is done, the

resistance of the support is greatly lowered, with a consequent gain in eiflciency. Under these circumstances, the section of line of increased diameter would be followed by the choke-linechoke system 46-51 to terminate the line, as has previously been described. A second gain is also accomplished, in that the voltage to the input choke 46 is now muchlower, and the losses in this choke are thereby reduced.

However, the increase in diameter of support Ill may be sufiicient to permit the interior of the enlarged portion to be used as the input choke by removing the rear wall 99 of the enlarged portion 98 to provide a choke loll opening toward the load, as shown in Fig. 11. The second orload choke ml is then reversed for symmetry and for ease of establishing the required quarter wave line section I I12 between the chokes. The anode chokes Hi3 and I04 may also be reversed, with comparable results. The mode of operation of the tube in any case is the same, and full D.-C. insulation is maintained, with the desired high impedance line termination accomplished.

Before passing to the discussion of the operation of the tube, it will be desirable to discuss the geometry of the resonators with relation to the filaments. The anode resonator may be di mensioned to be exactly five quarter wavelengths long. Thus, when this resonator is properly energized, there will be standing waves produced on the walls thereof. The filaments, grid slots, electron path, and the anode impact area are all positioned to straddle a standing wave voltage loop, with the region of maximum voltage approximately in the plane at a right angle to the axis of the tube dividing the filaments in half. Thus, there will be half of the axial extent of the filaments on one side of the standing wave loop peak, and the other half on the other side of this loop peak, thus placing peak voltages in the region of maximum filament emission. A preferred relationship is to make the filaments extend axially somewhat less than a quarter wavelength.

The filament and the grid slots may have their midpoints located one or more half electrical wavelengths distance away from the open end of the resonator to obtain fairly accurate registration of the peak of the standing wave voltage loop with the central plane of the filaments. I

prefer, however, that the central plane of the filaments be a single half Wavelength away from the open ends of the resonators. Thus, in the described tube the central plane of the filaments will be one electrical one-half wavelength away from the open ends of the resonators and three electrical quarter wavelengths away from the closed ends of the resonators, as it will be remembered that the choke system adds one quarter wavelength to the closed end of each resonator. I

I prefer to utilize the single half wavelength spacing of the filaments from the open ends of the resonators, because under these conditions the tube cannot easily operate at any lower frequency than the desired frequency. The only other frequency at which the tube might readily oscillate, with the central plane of the filaments a single half wavelength away from the open ends, would be a double frequency. However, as a practical matter, the possibility of such operation is remote unless the anode voltage were to be properly increased to give the proper electrode work period for the higher frequency.

5 The open resonator ends are also important in 11 I that they establish symmetry for the tube, prevent parasitic oscillations, and stabilize thestanding wave patterns axially along the resonators and consequently over the filaments and grid slots with equal voltages in planes at right angles to the axis of the tube.

Tuning of the filament resonator by movement of the grid choke system is such as to tune this resonator to provide a low inductive reactance.

If the circuit thus presented be analyzed, a tuned-filament, tuned-anode circuit is provided, with the anode and the cathode resonators coupled only by the anode-cathode capacity and with the grid as an untuned D.-C. biased structure floating at R.-F. potentials induced in it by the fields in the anode and cathode resonators. If, as in the structure shown, the filament circuit is made to have an inductive reactance small in relation to the capacitative reactance between anode and cathode, we have a condition set up where the R.-F. grid and anode voltages, with respect to the cathode, are in phase with respect to each other when the anode voltage is adjusted to operate the tube on an R.-F. half- .cycle electron work period, or by proper phasing of voltages with a work period of a multiple of half-cycles, although a single half-cycle work period is preferred. This work period is not necessarily the actual electron transit time,'but may be more truthfully considered as the period elapsing between the time of maximum emission from the filaments and the time of maximum work erformed by the emitted electrons on the load field. With a half-cycle R.-F. work period and with the reactances properly related, the filaments will be negative when both grid and anode are positive. For the next half-cycle this condition will be reversed, so that both grid and anode will be negative when the filaments are positive. Under these conditions, therefore, and under this mode of operation, there will be extremely high emissions take place from the negative filaments when the grid and anode are simultaneously positive, and eflicient electron cut-offs when .the grid and anode portions are both negative with the filaments positive.

The anode in the present tube and circuit operating in the manner described, therefore, has the novel function of effectively performing in the same manner as an accelerator grid in a tetrode, only however when accelerations are desired. Furthermore, this acceleration function diminishes or disappears during the interval when accelerations are not wanted. Thus, both anode and grid cooperate in starting and preventing electron emission. Extremely large amounts of oscillating power are thus produced.

Feedback is entirely capacitative. Consider the anode and filament voltages with respect to the grid voltage. The present filament and its support system is completely shielded from the anode by the grid, except at the grid slots. The filament voltage need not be 180 out-of-phase with the anode voltage, as would be the case were a skeleton grid to be inserted between the filament and anode, as will later be described. Instead, the filament voltage may be given almost any phase angle between zero and 180 with respect to the anode voltage, by a suitable choice of the grid-filament impedance, which is in series with the filament-anode capacitative reactance and driven by the voltage between the grid and anode.

If, however, it may be felt desirable to increase the coupling and still. maintain a fixed phase angle of nearly between anode and cathode voltages, then electromagnetic coupling between cathode and anode resonators may be resorted to.

In case it may be found desirable to use electromagnetic feedback between the anode resonators and the grid resonators t6 increase coupling, I may desire to provide a variable feedback in the form of a coupling loop I00, as shown in Fig. 5, this coupling loop being attached to a coupling transmission line Ill extending laterally from the anode 31 preferably at a voltage node, the central conductor N2 of the coupling transmission line 56 extending through the space between the grid and anode, through an aperture H3 in the grid 30, and then returning through this same aperture to contact the outer conductor of the line. The coupling loop is tuned by providing a conductive closure I H to the transmission line, this closure being movable along the central conductor through the medium of a bellows H5 and adjusted by screws 6 as to position along the line.

The standing wave pattern on coupling line I l I can thus be varied by varying the position of closure Ill and any desired amount of feedback passed through the loop llll.

If, however, only a fixed electromagnetic feedback is needed, the device shown in Fig. 6 may be used. Here the opening 3 is provided in grid 30 with a fixed loop ll! attached to one side of this opening and entering both grid-cathode and grid-anode spaces. The size of the coupling loop willdetermine the amount of feedback.

It will be seen from the foregoing description that the modification of the tube of my invention just described embodies two resonators having a common wall, 1. e., the grid, and that the grid slots are positioned in this common wall with the filament as a part of a facing wall. It will also be clearly seen that the operation of the tube as an oscillator relies upon the establishment of a standing wave pattern in boththe anode resonator and the cathode resonator. It follows, therefore, that the standing waves on the grid wall facing the cathode elements are actually closely alike and may, in some instances, be actually alike and register both as to position and strength, with the pattern on the grid wall facing the anode. When such registry occurs, there is no need for the grid surfaces-other than the field determining portions of the grid closely adjacent the filaments. When such registry occurs, all portions of the grid may be removed, except those portions immediately adjacent the filaments, to allow the identical resonator fields to merge.

If, for example, we call those portions of the grid 30 adjacent the filaments utilized for the concentration of the anode field on the filaments 25, the control surfaces, and if we call the re: maining material of the grid 30 the shielding surfaces, we can see that the presence of the shielding surfaces between the cathode structure and the anode is only useful in case the standing wave patterns are unlike in strength and position on each side thereof. When the field strengths are alike all along the resonators, the shielding surfaces can be completely removed and the tube will operate exactly as if such surfaces were present with only a slight change in basic frequency.

However, even if the standing waves along the resonators are not alike, if the standing wave conditions in the neighborhood of the filaments are alike, then the grid shielding surfaces can be removed and the tube will still oscillate, although under these conditions there will be a more substantial change in frequency.

The removal of the shielding grid surfaces can be accomplished by the provision of a skeleton grid, this grid being designed to give the proper ratio of capacity between grid and the anode and the grid and the cathode. The grid under these conditions may be considered as an intermediate point between two condensers, and the grid may be shaped to divide the voltage in a. proper ratio with the anode voltage nearly 180 out-of-phase with the cathode voltage. Obviously, this capacity ratio will be different for different tubes and is fixed for a given set of conditions.

The main difference, therefore, between the use of the grid-shielding surfaces and the omission thereof, is that when the grid-shielding surfaces are used, the cathode and anode circuits are separated and can be separately tuned, thus making the tube more fiexible in operation. However, for any fixed set of conditions, the grid-shielding surfaces can be completely removed and the tube will still oscillate, with the voltages still divided in the proper ratio and phase.

In Fig. '7, I have shown such an embodiment of my invention. All of the grid surfaces have been removed except those surfaces which are necessary for the application of the D.-C. bias field to distribute the anode field on the filaments. In this case, the filament supports, the filament flanges, the filaments, and the cathode resonator element I are all made exactly as before. The anode is as before, but in this case the R.-F. closure of the single resonator remaining is perfected by a single quarter wave choke system I30, this system being mounted on the outer filament support It. The choke elements extend outwardly with the cylindrical portions 50 thereof positioned concentric with the anode wall in the proper position to electrically close to R.-F. the single physical resonator remaining, at five quarter wavelengths with, as before, full D.-C. insulation. The grid has been reduced to a mere skeleton, comprising an outer grid flange I3I and an inner grid flange I32 joined by parallel grid wires I34 with one of these wires positioned on each side of each filament 25 and slightly toward the anode from the filaments. These wires take the place of the slot edges in the previously described modification. Proper voltage division is provided by the extent of grid flanges I3I and I32 toward the anode.

The grid skeleton is preferably supported by support arms I35 extending through openings I36 in one wall of the resonator. These openings are surrounded by support transmission lines I31 in which are positioned quarter wave choke-linechoke systems I38 to prevent radiation losses along the grid arms, exactly as described for the resonators. The grid support arms I35 may be supported by insulating discs positioned beyond the outer choke. Thus, the grid bias may be supplied to the grid skeleton through one or all of the support arms.

Except for the manner by which the voltages are established, the tube just described will oscillate in exactly the same mode as the tube previously described, in exactly the same manner as if the shielding surfaces of the grid were present.

An analysis of this last-mentioned tube will show, therefore, that the grids in the tubes and circuit described in this application have two separate functions. The first important function of the grid in both tubes herein described, is to so modify the D.-C. field between anode and cathode as to distribute this field on the filaments by virtue of the D.-C. bias placed on the grid. The second function of the grid is to permit, in the first embodiment shown, the standing wave fields to be unlike in strength inside and outside the grid conductor, and to permit them to be deliberately made unlike by tuning to adjust 4-f. voltage relationships. If the standing waves are, however, alike and registered even though only in the neighborhood of the grids, the shielding portions of the grid can be removed without affecting the oscillation of the tube in any manner, provided the biasing field remains. Even though slightly unlike, the voltages can be adjusted by proper grid skeleton disposition.

I would like to point out, however, that the particular means of supporting the grid structure, shown in the tube of Fig. 7, is only a. preferred means. Other equivalent arrangements may be utilized to support the grid within the tube. I,

would further like to point out that the use of parallel grid wires for determining the bias field is also not to be held a limitation, as other types of grid structure, such as a cylindrical mesh screen, may be utilized around the filaments and will perform in an essentially similar manner. The main considerations to be taken into account in designing a tube of the type shown in Fig. 7, are that D.-C. field determining grid elements are to be left within the tube, these grid elements properly disposed to divide the standing wave voltages in the same manner as if the gridshielding surfaces were to be present.

Thus, it will be seen that, reduced to its lowest terms, the tube of my invention as shown and described herein is of relatively simple structure, and, if desired, can be reduced to the basic form of a single resonator, this resonator acting as a coupled cathode and anode resonators.

In Figs. 11 and 12, I have shown a modification of the tube of my invention as constructed for use in a grounded-grid circuit, and arranged to be continuously pumped by a vacuum connection to the grid. Furthermore, this modification of my invention, as will be more fully pointed out later, utilizes a lateral rather than axial arrange ment of choke-line-choke elements in the anodegrid resonator.

Power may be taken out of the tube without reducing the effective anode-grid spacing, thus preventing spark-overs at high anode potentials. It will be noticed in this regard that in the tube of Fig. 1, the effective anode-grid spacing is reduced by the projection of the inner conductor 62 of the output transmission line into the anoderesonator space. This is eliminated in the tube of Figs. 11 and 12. Furthermore, in the tube of Figs. 11 and 12, electrons discharge through the anode and are picked up by the back of the anode, thus preventing the formation of hot-spots on the anode wall. In these figures, all elements not new to the arrangement have been given numerals corresponding to the numerals previously used for the same parts.

Referring to Figs. 11 and 12 for a more detailed description of this modification of my invention, concentric inner and outer filament supports I0 and I6 are provided, as in the previous embodiment, and these supports may be, if desired, water cooled in exactly the same manner as previously described, except that in this case expansion loops I2 may be dispensed with.

The filaments 25 are supported on one end thereof by blocks 200 attached to the inner filament support flange l4 by a plurality of spaced 7 layers of resilient fins 20I, so that the filaments can expand and contract during heating without exerting pressure between filament supports I and I6.

Due to the resilient filament connection, inner and outer filament supports can be sealed together by the use of spaced annular insulating rings 202 and 203, such as of glass or ceramic, separated by a rubber ring 204. These rings are slidably positioned around the inner filament support I0 and spaced from the fixed base of the outer cathode choke 21 by a short spacing sleeve 205. A long spacing sleeve 206 is then led outwardly along support I0 and slidable thereon to contact an outer glass ring 201 spaced from a second outer glass ring 208 by a second rubber ring 209.

Pressure is applied to force filament support I0 outwardly, through a glass pressure ring 2I0 outside of the tube, forced against the end of filament supp rt I0 by the usev of screws 2| I threaded through a connection block 2I2 fastened to the inner filament support I0. The pressure applied by screws 2I I forces the glass elements of two sets of glass rings together, thus expanding the intermediate rubber rings against filament support I0 and a sealing sleeve 2 I4 inwardly attached to outer filament support I6. An eflective and vacuum tight seal between the inner and outer filament supports I0 and I6 is thus procured, The inner and outer cathode supports are firmly tied together and, due to the resilient support of filaments 25, filament breakage during tube transport is eliminated.

The grid proper is shaped and positioned similarly to the grid 30 in the tube of Fig. 1, but in this case grid 30 is supported on a lateral flange 2 I 5, which in turn is supported by a heavy frame 2 I6, this frame being connected to filament support flange I9 by a glass cylinder 2I'I, thus completing the tie-up between the grid and the filament supports. A choke-line-choke system 26-21 is provided in the space between the outer filament support I6 and the grid 30, as in Fig. 1, and the space between filament support flanges I4 and 2| is shorted to R.-F. by quarterwave cylinder 2 I 8.

Attached to the outside of the grid 30 above the lateral flange 25, is a second lateral grid flange 220 extended outwardly in steps to support a cylindrical glass anode insulator 22I, the top of which is closed by an anode disc 222, through which pass a plurality of internally looped water cooling pipes 224, the ends 224' of these loops being welded to anode cylinder 3'! closed by anode dome 38.v Adjacent pipe loops 224 are connected on one side by anode material, and each connected pair of loops are spaced so that the spaces come opposite the grid slots and the filaments. Thus, the electrons emitted from the filaments, afterbeing decelerated, pass between adjacent loops of the water cooling pipes into the space 225 between the anode 31 and the glass cylinder The glass charges up and repels the electrons, which are then collected by the outer surface of the anode and the pipes themselves. Inasmuch as the electrons become widely dispersed within this space, no hot-spots can appear on the anode at any point.

I Anode potential is supplied to the anode disc 222 through connection 226. Inasmuch as it is desired to operate the grid of this tube at ground I prefer to terminate the anode resonator in an inner quarterwave choke and line section A followed by an annular quarterwave line B; a choke C followed by a quarterwave line D; backed up by a quarterwave choke E, line F and final choke G, these lines and chokes beingannularly disposed rather than axially disposed as in the tube of Fig. 1.

Such a termination of the anode resonator permits the power take-off loop GI to be inserted through the stepped flange 220 of the grid at a region of maximum current in the first choke A, which is also a part of the anod resonator.

Thus, the take-off conductor 62 does not pass a grounded grid circuit. Such circuits enable the tube to be utilized at high powers with signal modulation, as for example when large amounts of signal modulated power are desired.

I have found that great difficulty has heretofore been experienced in providing a proper and accurate measurement of the absolute power out put of high power tubes such as I have described operating at short wavelengths. I have therefore shown in conjunction with the output circuit of my tube, a means whereby the total power output of the tube may be quickly and easily measured. Fundamentally, I provid a high loss branch transmission line which may have, for example, a resistive element heated by the power absorbed in the line, with calorimetric measurement of the heat produced. One such means for high powers is shown in Fig. 14. For this purpose I provide a branch transmission line I50 on output transmission line 6|, having a composit normally non-conductive inner element comprising an outer glass tube I5I and an inner glass tube I52. The branch transmission line I50 may be made any odd number of quarter wavelengths, preferably one or three quarter wavelengths long, so that when the inner portion is made conductive, th power of the tube output may be absorbed in the transmission line.

I preferably make the inner portion of this branch transmission line resistively conductive by circulating brine at a known rat through tubes I5I and I52 from a brine inlet I54 to a brine outlet I55, both the brine inlet and brine outlet being provided with thermocouples I55 and I51, respectively, connected in series. Theavailable load power of the tube will be dissipated in heat in th branch line I50, and will show up as a current in meter I58. As this current difference is a measure of the heat dissipation in the branch transmission line, the absolute power output of the tube may be readily calculated, as th volume of water heated will be known, and heat losses from the line-to atmosphere can be readily calculated or measured.

Such an arrangement need only be used when checking the power, as the brine may be followed by distilled water to clean the insulated pipes and then removed from these pipes. This will effectively remove the central conductor from the line, and no power will be absorbed.

The length of the branch line is dependent on the power to be absorbed. It should be of the proper length, if in quarter wave multiples, to transfer all the heat dissipated therein to the brine without boiling the brine.

However, if a continuous check of power output is desired, the line may be tuned to absorb only a small predetermined percentage of the load, the brine continuously circulated at a known rate and measured as to heat absorbed. Many variations and combinations of the two methods will be apparent to those skilled in the art. It will also be obvious that the power absorbing line may be attached directly to the tube anode, if desired, and that the dissipated line may use high resistance solid material cooled by nonconductive fluids.

I claim:

1. An electron discharge device comprising three substantially parallel disposed walls forming a pair of resonators having a common wall, adjacent physically closed ends and adjacent physically open ends, a radio frequency closure mounted on each of two of said walls and extending toward and spaced from the adjacent walls to maintain direct current space insulation between said walls, said common wall having an opening therein, and an electron emitting surface on one of said other walls presented and adjacent to said opening, said opening and said electron emitting surface being positioned to straddle a voltage loop between the ends of said resonators.

2. An electron discharge device comprising three concentric conductors, the two outer conductors having adjacent spaced physically closed ends and adjacent spaced physically open ends, a concentric skirt flange-mounted on two of said conductors, and extending between the inner and intermediate conductors and between the intermediat and outer conductors to terminate said latter conductors as radio-frequency resonators with direct-current space insulation, an electron emitting surface mounted on said inner conductor, said intermediate conductor having an opening adjacent and registering with said electron emitting surface.

3. An electron discharge device comprising three concentric conductors, the two outer conductors having adjacent spaced physically closed ends and adjacent spaced physically open ends, a concentric skirt flange-mounted on two of said conductors, and extending between the inner and intermediate conductors and between the intermediate and outer conductors to terminate said latter conductors as radio-frequency resonators with direct current space insulation, a plurality of axially extending cathode mounted in concentric relation on said inner conductor, said intermediate electrode having a plurality of axially extending-slots registering in radial spaced relationship with said filaments.

4. Apparatus in accordance with claim 3 wherein said inner conductor is concentrically;

divided to provide paths for conductive heating of said filaments.

5. Apparatus in accordance with claim 3 wherein said concentric skirts form quarterwave terminations of said resonators.

6. Apparatus in accordance with claim 3 wherein said concentric skirts form quarterwave terminations of said resonators, and wherein each of said concentric skirts is outwardly backed by additional quarterwave concentric skirts spaced by a quarterwave line section.

'7. Apparatus in accordance with claim 3 wherein said slots and said filaments are positioned to straddle a voltage loop in said resonators.

8. Apparatus in accordance with claim 3 wherein said conductors are joined, positioned and sealed by connecting insulating-elements outside of said concentric skirts.

9. Apparatus in accordance with claim 3 18 wherein a transmission line is connected to. the outer conductor only, with a, central conductor positioned in said line, entering said outer condgctor and reflexed to contact the wall of said 1 e.

10. An electron discharge device comprising concentric outer anode and inner grid conductors having adjacent physically open ends and adjacent physically closed ends, a pair of concentric cathode conductors positioned concentrically within the grid conductor, one of said cathode conductors being longer than the other, parallel laterally extending flanges mounted on said cathode conductors, a, plurality of equally spaced circumferentially positioned filaments extending axially to connect said flanges, said filaments being positioned adjacent the inner surface oi. said grid conductor, said grid conductor having axially extending slots therein registering with the extent of said filaments, a cathode radio-irequency resonator closure flange mounted on said cathode conductors, a concentric skirt mounted on said flange and spaced from said grid conductor, an anode radio-frequency closure flange mounted on said grid conductor, a concentric skirt mounted on said latter flange and spaced from said anode conductor, and insulating elements joining said cathode conductors, said grid conductor and said anode conductor outside of said flanges.

11. Apparatus in accordance with claim 10 wherein said filaments and slots are positioned to straddle a voltage loop between the physically closed ends of said grid and anode conductors and the radio-frequency closure of said physically open ends by said flanges and skirts carried thereby.

12. Apparatus in accordance with claim 10 wherein said filaments and slots are positioned to straddle a voltage loop between the physically closed ends of said grid and anode conductors and the radio-frequency closure of said physically open ends by said flanges and skirts carried thereby, said voltage loop being one or more half wavelengths away from said physically open ends.

13. Apparatus in accordance with claim 10 wherein said filaments and slots are positioned to straddle a voltage loop between the physically closed ends of said grid and anode conductors and the radio-frequency closure of said physically open ends by said flanges and skirts carried thereby, said voltage loop being one-halt wavelength away from said physically open ends.

14. In an oscillator circuit utilizing a triode tube having a cathode completely shielded from an anode by a single grid except for intermediate grid openings in said grid, means for supplying a D.-C. potential to said cathode with said anode at ground potential, a tuned cathode circuit, a tuned anode circuit, and a substantially reactance-free grid circuit connected together and to the respective electrodes, the inductive reactance of said cathode circuit being less than the capacitative reactance of the cathode-anode interelectrode capacity to provide capacity feedback for self-sustaining oscillations with the grid and anode radio-frequency potentials at least partially in phase with relation to said cathode.

15. An oscillation generation circuit comprising the tube of claim 10, an anode transformer having a secondary connected to said filaments and to said anode with said anode grounded, a resistance between said transformer and said filament connection; and a, connection between said grid and said resistor means for heating said filaments to cause electron emission therefrom, the voltage of said anode being controlled to cause said tube to oscillate on a, half-cycle electron work period when said radio-frequency closures are positioned on their respective electrodes to dimension the coextensive resonators to substantially an odd number of quarter wavelengths.

16. An oscillation generation circuit comprising the tube of claim 10, an anode transformer having a secondary connected to said filaments and to said anode with said anode grounded, a resistance between said transformer and said filament connection, and a connection between said grid and said resistance, means for heating said filaments to cause electron emission therefrom, the voltage of said anode being controlled to cause said tube to oscillate on a half-cycle electron work period when said choke flanges are positioned on their respective electrodes to dimension the coextensive resonators to substantially an odd number of quarter wavelengths with the peak of a voltage loop between the ends of the coextensive resonators positioned approximately midway between the ends of said filaments.

17. An oscillation generation circuit comprising a triode tube having an anode shielded from a cathode by a single grid except for intermediate grid openings in the same grid, a resonant circuit having one end connected to said cathode, a resonant circuit connected at one end to said anode, the other ends of said circuit being connected together, a substantially reactance-free connection from said grid to said connected ends, means for impressing a direct current potential between said cathode and anode with said anode grounded, said potential being such as to provide a half-cycle electron work period, the openings in said grid being proportioned to provide an inductive reactance in the cathode circuit smal1 in relation to the capacitative reactance between anode and cathode thereby causing said tube to oscillate by the feedback due to anode-cathode capacity only.

18. .An oscillation generation circuit comprising a triode tube having an anode shielded from a cathode by a single grid except fo intermediate grid openings in the same grid, a resonant circuit having one end connected to said cathode, a resonant circuit connected at one end to said anode, the other ends of said circuit being connected together, a substantially reactance-free connection from said grid to said connected ends, means for impressing a direct-current potential between said cathode and anode with said anode grounded, said potential being such as to provide a halfcycle electron work period, the openings in said grid being proportioned to provide an inductive reactance in the circuit cathode small in relation to the capacitative reactance between anode and cathode thereby causing said tube to oscillate by the feedback due to anode-cathode capacity only with a half-cycle electron work period.

19. An oscillation generation circuit comprising a triode tube having an anode shielded from a cathode by a single grid except for intermediate grid openings in the same grid, a resonant circuit having one end connected to said cathode, a resonant circuit connected at one end to said anode, the other ends of said circuit being connected together, a substantially reactance-free connection from said grid to said connected ends, means for impressing a direct-current potential between said cathode and anode with said anode grounded, said potential being such as to provide a half-cycle electron work period, the openings in said grid being proportioned to provide an inductive react- 20 ance in the circuit cathode small in relation to the capacitative reactanc between anode and cathode thereby causing said tube to oscillate by the feedback due to anode-cathode capacity only with an electron work period of one or more halfcycles.

20. A self-resonating electron discharge triode tube having an inner cathode resonator element and an outer anode resonator element, an electron emittin'g section forming a part of said oathode resonator element, and a, singe field modifying meansbetween said electron emitting section and said anode resonating element, adjacent said electron emitting section only.

21. Apparatus in accordance with claim 20 wherein said resonator elements are substantially an odd number of quarter wavelengths long.

22. Apparatus in accordance with claim 20 wherein said resonator elements are substantially an odd number of quarter wavelengths long with said electron emitting section axially straddling a voltage loop position.

23. Apparatus in according with claim 20 wherein said resonator elements are substantially an odd number of quarter wavelengths long with said electron emitting section axially straddling a voltage loop position and of less than onequarter wavelength axial extent.

24. Apparatus in accordance with claim 20 wherein said field modifying elements are confined to the immediate neighborhood of said electron emitting part of said cathode resonator element and have capacity dividing portions extending toward said anode only.

25. Apparatus in accordance with claim 20 wherein said resonator elements are substantially an odd number of quarter wavelengths long with said electron emitting section axially straddling a voltage loop position one-half wavelength from one radio-frequency end of said resonator elements.

26. In a self-resonating oscillator tube having inner, outer and intermediate space insulated conductors having adjacent physically closed ends and opposite physically open ends and means for passing electrons from said inner to said outer conductors, means for closing said physically open ends comprising a quarter wave hollow resonator section mounted on each of two of said conductors and extending toward the facing conductors, said resonator section extending between a voltage loop and a current node during operation of said tube.

27. Means for terminating a radio-frequency transmission line having inner and outer conductors spaced by direct current insulation, comprising a quarterwave anti-resonant choke positioned on one of the conductors of said line followed by a second quarterwave anti-resonant choke spaced by a quarterwave line section from said first choke.

28. Apparatus in accordance with claim 27 wherein said chokes are toroidal chambers bridging a physical cut in one of said conductors.

29. Apparatus in accordance with claim 27 wherein said chokes are cylinders positioned on one of said conductors by end flanges, the other end of said cylinders being open, with said cylinders close to and concentric with the other conductor.

30. In combination with a main concentric transmission line carrying high frequency power, a high loss transmission line connected to said main transmission line at a current loop,'said branch transmission line being of an odd number 21 of quarter wavelengths long with respect to the wavelength of the standing waves in said line to absorb power therefrom, and means for measuring the heat liberated in said branch transmission line.

31. In combination with a main concentric transmission line carrying high frequency power, a high loss transmission line connected to said main transmission line at a current loop, said branch transmission line being dimensioned to absorb a predetermined percentage of the power carried by said line, and means for measuring the heat liberated in said branch transmission line.

32. In combination with a main concentric transmission line carrying high frequency power, a branch transmission line connected to said main transmission line at a current loop, said branch transmission line being dimensioned to absorb a predetermined percentage of the power carried by said line, the central element of said branch transmission line being normally non-conductive,

means for making said central element conductive at will, and means for measuring the heat liberated in said branch transmission line while conductive.

33. In combination with a main concentric transmission line carrying high frequency power, a branch transmission line connected to said main transmission line at a current loop, said branch transmission line being dimensioned to absorb a predetermined percentage of the power carried by said line, the central element of said branch transmission line being a hollow insulating element, means .ior flowing a conductive fluid through said central element at will, and means for measuring the heat 01 the fluid passing through said central element.

34. Apparatus in accordance with claim 33 wherein said branch transmission line is an odd number of quarter wavelengths long to absorb all the power in said main transmission line.

35. Apparatus in accordance with claim 33 wherein said branch transmission line is an odd number of quarter wavelengths long to absorb all the power in said main transmission line, and wherein said fluid is a conductive brine.

36. An electron discharge device comprising three substantially parallel disposed walls forming a pair of resonators having a common wall, said common wall having an opening therein, and an electron emitting surface positioned in one of said resonators opposite said opening, said opening and said emitting surface being positioned to straddle a voltage loop between the ends of said resonators.

DAVID H. SLOAN. 

